1. Field of Invention
This invention pertains to the art of methods and apparatuses for injection molding, and more specifically to methods and apparatuses for a modular injection molding machine.
2. Description of the Related Art
Injection molding machines are commonly used in the manufacturing industry. They use a clamping apparatus to hold a mold closed during injection and an extruder/injector to fill a cavity in the mold with an elastomeric material such as rubber or plastic. Typically the elastomeric material is then cured before it is removed from the mold so sometimes these machines are known as presses. There are two main types of clamping apparatuses currently on the market. The first type uses a C frame structure to carry the load which is generated in the closing or opening of the clamp. The second type uses posts or a frame in which the load is located on the same plane with the axis of the frame. A commonly known example of this is a four post press which has the clamp load located in the center of the four posts.
A common problem often encountered in the art deals with the need to expand an existing injection molding machine by adding another clamping apparatus. Typically, an entire new machine must be purchased. Modular machines are available but they only provide room in precise and predetermined locations for the addition of another clamping apparatus. These options are expensive and inflexible.
A problem in the art with the post clamping apparatus is that the posts increase the width of the machine and also requires additional floor space. This limits the minimum center to center distance of an adjacent clamping apparatus. If a part is required with molding at two or more distinct sections, the presses might not be able to be located sufficiently close to each other. This requirement is known in the automotive door seal industry where one part is molded to a second part which is then molded to a third part. One known solution to this problem is to purchase and use a larger press so that both molding can be accomplished at once. Another known solution is to make the molding one at a time. The first solution is quite expensive and the second solution increases inventory, material handling costs and production time due to the transporting requirements.
Another problem with the post clamping apparatus is limited mold accessibility. A post clamping apparatus has, at the most, two completely accessible sides (a two post press).
A problem in the art with the C frame clamping apparatus is the relatively large bending load felt by the C frame. This bending load is a function of the distance between the tips of the "C."
Another problem encountered in the art with both types of clamping apparatuses deals with the common use of a shuttle which moves molds in and out of the press. Typically, a shuttle requires a complex and relatively expensive system of interlocks and motion devices.
Another problem with shuttles is as follows. Typically, on a shuttle press one part is being made (injected and/or cured) in one mold while another part is being loaded or unloaded into a second mold. The problem occurs when the load/unload time of the second mold is less than the injection/curing time of the first mold. When this occurs the operator is not being used at full potential because the operator must wait for the completion of the injection/curing stage of the first mold. The only known solution to improve the productivity of the operator is to purchase a second machine for the operator to operate concurrently. This solution is expensive and typically means that the operator will have a relatively long distance to travel between the two machines.
Still another problem known in the art is that the extruder/injector is often under utilized. After one part has been injected into the mold cavity, if the extruder/injector cannot immediately begin injecting another part it remains idle, wasting the relatively large investment put into it (typically the extruder/injector cost will be about 30% of the total machine cost).
The present invention provides methods and apparatuses for eliminating or reducing these problems. The difficulties inherent in the art are therefore overcome in a way which is simple and efficient, while providing better and more advantageous results.